1. Field of Invention
The invention relates to an antenna, and, in particular, to a printed antenna and a printed antenna module.
2. Related Art
The rapidly developed radio transmission has brought various products and technologies applied in the field of multi-band transmission, such that many new products have the performance of radio transmission to meet the consumer's requirement. The antenna is an important element for transmitting and receiving electromagnetic wave energy in the radio transmission system. If the antenna is lost, the radio transmission system cannot transmit and receive data. Thus, the antenna plays an indispensable role in the radio transmission system.
In the radio transmission system, the currently used frequency band specifications include IEEE 802.11, IEEE 802.15.1 (bluetooth communication), and the like. IEEE 802.11 is further divided into the specifications of IEEE 802.11a, IEEE 802.11b and IEEE 802.11g. IEEE 802.11a is the specification corresponding to the frequency band of 5 GHz. IEEE 802.11b and IEEE 802.11g are the specifications corresponding to the frequency band of 2.4 GHz. IEEE 802.15.1 is also the specification corresponding to the frequency band of 2.4 GHz.
To meet the above-mentioned specifications, the printed antenna is frequently used. As shown in FIG. 1, a conventional printed antenna 1 includes a substrate 11, a grounding portion 12, a radiating portion 13 and a feeding portion 14. The substrate 11 has a surface 111, on which the grounding portion 12, the radiating portion 13 and the feeding portion 14 are disposed. The grounding portion 12 is electrically connected with the radiating portion 13. The feeding portion 14 disposed in parallel to the grounding portion 12 is electrically connected with the radiating portion 13.
In addition, the peak value of the power gain of the printed antenna 1 is about 2 to 3 dBi. However, the power gain provided by the current printed antenna 1 is insufficient and thus induces some problems as the consumers gradually pay attention to the communication quality. For example, because the power gain of the printed antenna 1 is not large enough, the manufacturer typically enhances the signal receiving and transmitting ability of the printed antenna 1 by amplifying the information that is received or transmitted by the printed antenna 1. However, the received or transmitted noise is correspondingly amplified, and the communication quality cannot be enhanced and the power loss is also increased. Also, if the printed antenna 1 is used in the diversity application such as the spatial diversity, the polarized diversity or the radiation pattern diversity, the correlation between the channels in the space is too great, and the communication quality is thus deteriorated.
Thus, it is an important subject of the invention to provide a printed antenna with an enhanced power gain.